Modulating system



MODULAT ING SYS TEM Filed Dec. 21, 1931 gas l6 //9 INVENTOR,

ATTORNEY LPH M. HE/NTZ. B MKW Patented Apr. 17, 1934 MODULATING SYSTEM Ralph M. Helntz, Palo Alto, Calm, assignor to Hcintz & Kaufman, Ltd., San Francisco, Calif., a corporation of Nevada.

Application December 2 14 Claim.

This invention relates to modulating systems, and particularly to systems for modulating the output of a high frequency generator or frequency multiplier of the type described in my 5 copending appplication, Serial No. 574,262, filed November 11, 1931.

Among the objects of my invention are: To provide a source of modulated polyphase current; to provide a modulating system which is not limited as to the frequencies which it will modulate; to provide a modulating system which is equally effective on high and low modulating frequencies; and to provide a modulating system wherein the modulating circuit may be entirely isolated electrically from the circuit carrying the modulated current and in which the reaction between the output and the input circuits is substantially nil.

Other objects of my invention will be apparent or will be specifically pointed out in the descrip- .20 tion forming a part of this specification, but I do not limit myself to the embodiment of my invention herein described, as various forms may be adopted within the scope of the claims.

Referring to the drawing:

Figure 1 is a diagram, largely schematic, showing a high frequency generator of the type described in my copending application above referred to, together with a circuit for modulating the output of the generator in accordance with my invention.

Figure 2 is a transverse section of the generator shown in Figure 1, illustrating the effect of the modulating system mentioned.

The high frequency generator to which this invention particularly refers comprises a vacuum tube having therein a suitable source of cathode rays. Positioned in the path of this source are a plurality of anodes, at least one of which comprises a plurality of spaced bars or elements.

Means are provided for deflecting the beam of rays from the cathode to the anode across these elements, this deflecting means being preferably actuated from a polyphase source so that the beam of rays traces a circular path. Broadly,

considered, the method of this invention comprises varying the concentration of the beam of cathode rays, thereby changing its cross section at its point of impact with the anode, so that it may either be entirely intercepted by one of the anode elements or, with a less degree of concentration, it will overlap a plurality of the elements and hence divide the current which it represents between a plurality of the anodes. The modulation then varies between two extremes, the alternating component of the output current being a 1, 1931, Serial No. 582,273 (01. 179-171) minimum when the cathode beam falls equally upon all of the anodes at the same time, and a maximum when the beam is so concentrated that it is entirely intercepted by each of the anodes in succession.

Describing a preferred form of the device in detail, the generator of the ray comprises an evacuated envelope 1 having a stem 2 which carries a cathode which may be of the filamentary type, but'which is shown as an emitting cylinder 3 surrounded by a heating coil 5. A battery 6 excites the heating coil through the leads 7.

At the end of the tube opposite the stem is a plurality of disk-shaped anodes whose form is best shown in Figure 2. As shown, the hindmost of these anodes 9 is a disk which is formed without apertures. Forward of this is a second anode 10, which is also of disk form but has sector-shaped openings 11 uniformly spaced. and radially arranged around the disk. These openings account for one-third of the total space around the disk. The foremost anode 12 has similar openings 14 formed therein, but these openings are twice the width of the openings in the anode 10. In this case, therefore, it is the count for one-third of the circle, the openings themselves accounting for two-thirds. It is, of course, possible to make each of the anodes of the form of the anode 12, each successive anode being displaced from alinement with the preceding one by the width of one of the anode elements or bars.

It will be seen that a beam of cathode rays, deflected in a circular path around the axis of the tube, will first pass through the openings in the two forward anodes to fall upon the anode 9, will next be intercepted by the anode 10, passing through the opening 14 in theanode 12 only, and will finally be intercepted by one of the elements of the anode 12, after which the cycle will be repeated. The three anodes connect to the three branches of a polyphase circuit, the anode 9 being connected to a coil 15, the anode 10 to a coil 16, and the anode 11 to a coil 1'7, the three coils being connected in star. The coils may be tuned by condensers 19 connected in delta. 7

It is to be understood that the output circuit arrangement just described is only one sample of many polyphase output circuit arrangements which may be used, these circuits being connected in star or delta in the well known manner in order to accomplish the particular result desired.

bars or spokes between the opening which ac- Connecting to the neutral of the star-connected output circuit is a suitable potential source 20, whose negative end connects to the cathode of the tube. An auxiliary anode 21, having a central perforation, is preferably arranged adjacent the cathode and is connected to an intermediate point on the source 20 through a lead 22. The function of this auxiliary anode is to apply a rapid acceleration to the rays from the cathode, and define the majority of the rays into a beam having a definite cross section at its point of leaving the anode 21.

Surrounding the tube is a set of deflecting coils 23, positioned equi-angularly about the coil and in planes parallel to its axis. These coils are energized by a polyphase alternating current from a suitable generator 25. Thus energized the coils produce a rotating uniform magnetic field which serves to deflect the beam of cathode rays in a circular path around the axis of the tube. Thus deflected the beam of rays will be intercepted by each of the anodes in turn as was just described, and a current will flow in the output circuit whose frequency is that of the generator 25 multiplied by the number of openings in the anodes 10 and 12.

The tube is surrounded by a coil or solenoid 26 which is coaxial with the tube and hence with the mean path of the cathode rays. The coil is supplied by leads 27 and 29 from a direct current source 30. A rheostat 31 is preferably provided for adjusting the strength of this current, both rheostat and source being preferably bypassed by a. condenser 32.

In series with the source and the coil 26 is the secondary 34 of a transformer whose primary 35 forms the output circuit of an amplifier 36. A microphone 3'7 is connected to the input circuit of the amplifier.

As has been described in my copending application, Serial No. 574,262 above mentioned, and in various applications of Philo T. Farnsworth, the effect of direct current in the coil 26 is to concentrate the beam of electrons to produce a sharp focus at a distance from the source which is inversely proportional to the current in the coil. There is an optimum current which will bring the beam to a sharp focus in the plane of the anode 12. Greater current will form the focus nearer to the cathode than this plane, while smaller current will focus the beam at a greater distance from the cathode, the beam where it strikes the anode plane then having a lesser degree of concentration.

In the present instance the rheostat 31 is so adjusted that the current supplied to-the coil is insufficient completely to focus the beam. Superposed upon the direct current component in the coil is alternating current at the desired modulating frequency supplied from the amplifier through the secondary 34 of the transformer. The adjustment should be such that with maximum current flowing, i. e., when the voice current boosts that from the source 30, the beam will be brought to maximum concentration and will be of a size approximately as shown by the dotted circle 39 of Figure 2. It will be seen that thus concentrated the beam is no greater in diameter than the width of the anode elements, and hence may be completely intercepted by any one of the anodes in turn.

' With zero voice current supplied from the amplifier, or with the voice current bucking the direct current from the source, the concentration of the beam is decreased, the trace of the beam on the anode structure being shown by the dotted line 40 of Figure 2. The total direct current flowing in the output circuit is unchanged by this change in concentration, but its diversion between the circuits is changed. If the circle becomes large enough so that substantially equal amounts of the cross-section of the beam fall on each of the three anodes, rotation of the beam around the axis of the tube will cause no change in currents to the three paths of the output circuit. It will therefore be seen that by changing the concentration of the beam the alternating component in the output circuit may be completely modulated, although the direct current component flowing in the neutral lead 27 remains unchanged.

It may be shown that modulating any of the flelds through which the electron beam flows will serve to modulate the output, my copending application, Serial No. 582,275, filed coincidentally with this application, describing in particular the effect of modulating the deflecting field. Furthermore, it is well recognized that there are other methods of changing the concentration or focusing of a beam of cathode rays, e. g., by means of electrostatic focusing. The conditions for electrostatic focusing are well known, and will not be described here. It will readily be seen that any method by which the concentration of the beam is altered at the modulating frequency will accomplish the result here described.

I claim:

1. The method of generating a modulated alternating current which comprises generating a direct current, converting said direct current to pulsating current by diverting a portion thereof successively to each of a plurality of paths, and modulating the alternating component of said pulsating current by changing the division of said direct current between said paths.

2. The method of generating a modulated polyphase alternating current which comprises generating a direct current, diverting at least a portion of said current successively into a plurality of paths each constituting a phase, and modulating said current by changing the maximum proportion of said current diverted to any one path, the limits of said modulation being the uniform distribution of the current between all paths at the same instant, and the diversion of all of the current into each of said paths successively.

3. The method of modulating an alternating current generated by deflecting a beam of cathode rays across a succession of anodes each connected to a different branch of a circuit, which comprises varying the distribution of said beam in accordance with the modulating signals between said anodes to vary the proportion of the cathode ray current which is converted into alternating current.

4. The method of modulating an alternating current generated by deflecting a beam of cathode rays across a succession of anodes each connected to a different branch of a circuit, which includes the step of varying the concentration of said beam in accordance with the modulating signals to change the proportion thereof which may be intercepted by any one of said anodes.

5. The method of generating a modulated alternating current with a vacuum tube apparatus comprising a cathode, a plurality of anodes across which a beam of rays from said cathode may be deflected, and means for concentrating said rays, which comprises varying said concentrating means in accordance with the modulating nals to change the proportion of said rays which may be intercepted by any one or said anodes.

6. The method of generating a modulated alternating current with a vacuum tube apparatus comprising a cathode, a plurality of anodes across which a beam of rays from said cathode may be deflected, and a coil coaxial with the path of said beam for establishing a magnetic fleld for concentrating said beam, which comprises the steps of passing a current through said coil and varying said current at the modulating frequency to change the proportion of said beam which may be intercepted by any one of said anodes. I

1 7. A generator of modulated alternating cur-- rents comprising a source of cathode rays, means for concentrating said rays to form a definitely defined beam, a plurality of anode elements each dimensioned to intercept substantially all of the concentrated beam, means for deflecting said beam across said anode elements successively, and means for varying the concentration of said beam at a modulating frequency to change the degree to which it may be intercepted by any single one of said anode elements;

8. A generator of modulated alternating current which comprises a cathode, a plurality of anode elements positioned opposite said cathode, a coil positioned to establish a magnetic field through which electrons traveling from said cathode to said anodes must'pass, means for deflecting said electrons across said anodes, and means for passing a current through said coil and for varying said current at a modulating frequency. 9. A generator or modulated alternating current which comprises a cathode, a plurality of anode elements positioned opposite said cathode, a coil positioned to establish a magnetic field coaxial with the path of a stream of electrons passing from said cathode to said anode elements, means for deflecting said electron stream across said anode elements, and means for passing a modulated current through said coil.

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10. The combination with a generator of alternating current comprising a cathode, an anode having a plurality of spaced elements, and means for deflecting a beam of cathode rays across said elements, of a coil mounted coaxially with said beam of cathode rays, means for passing a direct current through said coil, and means for modulating said current to vary the concentration of said beam of rays at the modulation frequency.

11. The combination with a generator 01' alternating current comprising a cathode, an anode having a plurality of spaced elements, and means for deflecting a beam of cathode rays across said elements, of means for .concentrating said beam of rays, and means for varying the concentration of said beam at a modulating frequency.

12. The combination with a generator of alternating current comprising a cathode, an anode having a plurality of spaced elements, and means for deflecting a beam of cathode rays across said elements, of a coil mounted coaxially with said beam of cathode rays, means for passing a direct current through said coil, and sound actuated means for modulating the current through said coil to vary the concentration of said beam.

13. The combination with a generator ot-alternating current comprising a cathode, a plurality of anodes one or which comprises a plurality of radially arranged bars, and means for deflecting a beam of rays across said bars in a substantially circular path, of means for concentrating said beam of rays, and means for varying the concentration of said beam at a modulating frequency.

14. The combination with a generator 01' alternating current comprising a cathode, a plurality of anodes one of which comprises a plurality of radially arranged bars, and means for deflecting a beam of ray across said bars in asubstantially circular path, of a coil mounted coaxlally with said beam of cathode rays, means for passing a direct current through said coil, and means for modulating said current to vary the concentration of said beam of rays at the modulation frequency.

RALPI-I M. HEINTZ. 

